1. Field of the Invention
The invention relates generally to retractable devices which have an operating element movable between an exposed, working position and a covered, storage position. More particularly, the invention relates to manually operable retractable surgical devices which have uniquely shaped operative elements capable of being extended from a retracted position to a selected extended position.
2. Description of the Prior Art
Retractable cutting devices for use in surgical procedures are commonly known in the prior art. The retractable nature of such devices assures that the working or cutting surface of the instrument will be held retracted within the device in such a way as to not interfere with the placement of the device at the work site to be operated upon. Very often the working or operative portion of the instrument is at the distal end of a generally longitudinal support member. When the distal end has been moved past or through areas which are interposed between the entry point of the instrument and the work site, the operative portion of the instrument, often a cutting surface, may be extended from its protective sheath in order to perform the desired surgical procedure without unintentionally injuring surrounding tissue.
The present invention is particularly adaptable to small cutting instruments and is, therefore, intended primarily for use in arthroscopy or microsurgery of the knee and other joints in humans (or other animals). Consequently, for explanatory purposes, the invention will be described in terms of an arthroscopic knife. It will be understood, however, that the principles of this invention are equally applicable to other surgical, and even non-surgical, cutting and non-cutting devices. For these reasons, the disclosed preferred embodiment of the invention and the use herein of terms such as "knife", "cutting", "blades" and the like should not be considered as limiting the scope of the invention.
Arthroscopy involves the use of viewing, probing and cutting devices that can be utilized through a very small opening in the patient's skin. The procedure necessarily involves the steps of insertion, retraction and manipulation of various instruments or devices through the skin to an area to be operated upon. Such steps are primarily blind until the device comes into view of the arthroscope positioned at the work site through another opening. Consequently, it is desirable that any cutting or other potentially dangerous instruments be protected from either unintentionally injuring the patient or from being damaged by other tools during the blind maneuvers. Retractable cutting devices are obviously quite desirable in arthroscopic procedures.
In addition to the desirability of retractable devices, it should be apparent that numerous shapes of operating elements are desirable. Surgical and other operating elements may obviously be provided with a variety of different profiles suitable for different tasks. In arthroscopic applications, for example, it is often desirable to have a surgical element curved in a plane transverse to the blade plane, such a shape being more suitable for certain procedures than a straight single or double-edge knife. Prior art arthroscopic knives are known which have transversely curved cutting edges wherein the curve of the cutting blade is established and guided by the curve of the flattened, curved guide sheath situated at the distal end of the instrument and within which the blade reciprocates between a retracted and an extended position. Known examples of such curved surgical instruments are the 3M Sheathed Knives available from the Orthopedic Products Division of the Minnesota Mining and Manufacturing Company.
One disadvantage associated with instruments having a blade reciprocable within a transversely curved sheath is that it is more difficult to insert such instruments into the desired work site. The curved sheath must be manipulated through what is essentially a straight longitudinal bore previously formed in the tissue by an arthroscopic obturator or trocar. This must be done with extreme care to avoid injuring portions of the body or joint interposed between the entry point of the instrument and the work site. Moreover, in some instances the surgeon may choose to utilize a rigid cannula or portal through which the instruments must be inserted. In these cases use of a curved sheath is impossible.
One of the concerns that must be addressed in all reciprocable cutting instruments is that the cutting edges of the operative element must be somehow spaced from adjacent surfaces of the protective sheath in order to prevent the cutting edges from being dulled during the extension and/or retraction of the element.
In view of the above, it is an object of this invention to provide a retractable surgical instrument having a curved operative element encased within a linear sheath.
It is also an object of this invention to provide a retractable surgical instrument having a curved operative element encased within a flattened linear sheath.
It is another object of this invention to provide a retractable surgical instrument having a curved operative element encased within a distally located, flattened linear sheath wherein the cutting edges of the element are spaced from the inside surfaces of the sheath during extension and/or retraction of the element.
It is still another object of this invention to provide a retractable surgical instrument having a curved operative element encased within a distally located, flattened linear sheath wherein an indication is provided at the distal tip of the instrument of the direction of curvature of the element.
It is yet another object of this invention to provide a retractable surgical instrument having a curved operative element encased within a flattened linear sheath wherein the curve of the element is such that the distal tip of the element will, in an extended position be situated beyond the plane of either broad side of the flattened sheath.